1. Field of the Invention
The present invention relates to a printer device having a thermal head for printing on paper and a platen roll for feeding paper to the thermal head.
2. Description of the Related Art
In a conventional printer, printing paper unwound from a roll of paper is nipped between a platen roller and a thermal head, and printing is carried out by heating the thermal head during the feeding of the paper. For example, Japanese Unexamined Patent Publication No. 3-199069 discloses a line thermal printer in which a rotational shaft of a platen roll is inserted into an U-shaped notch such that the platen roll may be precisely positioned relative to a head in the horizontal and vertical directions.
Japanese Unexamined Patent Publication No. 2004-114417 discloses a printer in which the center of a support shaft of a head for a platen is arranged on an extended head surface and the force of a spring for biasing the head to the platen is applied to the head in the direction perpendicular to the head surface.
Since it is necessary to regularly clean or replace a thermal head used in a thermal printer, it is preferable that the thermal head be easily detachable from a body of the thermal printer. However, it is necessary to precisely position the thermal head relative to a platen during use for printing quality. Therefore, it is not possible to easily make the thermal head detachable from the body. In addition, in recent years, it is desirable that one printer can print characters or the like with stable quality, on printing paper having different thickness' (in particular, thick paper).
In the line thermal printer described in Japanese Unexamined Patent Publication No. 3-199069, the platen is inserted into the U-shaped notch in order to improve the positional accuracy of the platen relative to the fixed thermal head. Therefore, when the thermal head is exchanged, it is necessary to detach the platen and then detach the fixed thermal head, which is troublesome. In the thermal printer described in Japanese Unexamined Patent Publication No. 2004-114417, as the thermal head is rotated about the support shaft, it is not possible to move the thermal head in the direction precisely perpendicular to the surface of the platen when printing paper having different thickness' are used. Therefore, the printing quality may be uneven depending on the thickness of the paper.